The long range goal of this project is to gain a precise understanding of the developmental processes involved in odontogenesis. Interaction of each of the two tissues involved, the odontoblasts and the ameloblasts, with the changing extracellular matrix (ECM) microenvironment which they build between themselves is believed to be extremely important in the continued differentiation of odontoblasts and ameloblasts. Dirct odontoblast-to-ameloblast contracts form at a particular state of differentiation and these contacts are also undoubtedly of importance for normal odontogenesis. We are using a variety of techniques to analyze ECM macromolecules present in odontogenesis, with ultrastructural cytochemical and immunocytochemical analyses of their precise location. We are also using freeze-fracture to analyze the junctional specializations of developing odontoblasts and ameloblasts. A very important new direction our work is taking is the production of monoclonal antibodies to antigens present in developing teeth. At the moment this work is limited to monoclonal antibodies to fibronectin, but we hope to expand our use of hybridoma technology in year 03 or in the competing renewal of this grant.